JP2008242338A - Charging roll for electrophotographic equipment and method for manufacturing charging roll for electrophotographic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging roll for electrophotographic equipment having a small diameter and low hardness, and to provide a method for manufacturing the electrifying roll for electrophotographic equipment. <P>SOLUTION: The charging roll 10 is constituted by successively layering a rubber elastic layer 14, a rubber tube layer 16 and a surface layer 18 on the outer circumference of a conductive shaft 12. The rubber elastic layer 14 and the rubber tube layer 16 come into contact with each other, and either or both of them contains lubricant. The ASKER C hardness of the surface of the roll in such a state that the rubber elastic layer 14 is formed is within 63 to 80, and the ASKER C hardness of the surface of the roll in such a state that the rubber elastic layer 14 and the rubber tube layer 16 are layered may preferably be within 65 to 82. The outside diameter of the roll may preferably be 12 mm or less. The method for manufacturing the charging roll includes a step for forming the rubber elastic layer 14 on the outer circumference of the conductive shaft 12 and covering the outer circumference of the rubber elastic layer 14 with the rubber tube 16, wherein the lubricant is contained in either or both of the rubber elastic layer 14 and the rubber tube 16. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a charging roll for electrophotographic equipment and a method for producing a charging roll for electrophotographic equipment.

  In recent years, electrophotographic apparatuses such as copying machines, printers, and facsimiles that employ an electrophotographic system have been widely used. Usually, a photosensitive drum is incorporated in an electrophotographic apparatus, and conductive rolls such as a charging roll, a developing roll, a transfer roll, and a toner supply roll are disposed around the photosensitive drum.

  In this type of electrophotographic apparatus, for example, a contact charging method is adopted in which the surface of the photosensitive drum is charged by bringing the roll surface of the charging roll into direct contact with the surface of the photosensitive drum. For this reason, the charging roll is required to have excellent chargeability and appropriate elasticity.

  In order to satisfy these required characteristics, for example, Patent Document 1 discloses a charging roll formed by extruding a rubber layer such as hydrin rubber on a shaft body and further forming a protective layer on the outer periphery thereof.

JP 2004-125823 A

  In recent years, miniaturization of electrophotographic equipment has been promoted, and accordingly, the diameter of the charging roll is required to be reduced.

  When the diameter of the charging roll is reduced, the contact area with the surface of the photosensitive drum is reduced. As a result, the charging performance deteriorates and image defects occur. Therefore, in this case, it is necessary to increase the contact area with the surface of the photosensitive drum, and for this purpose, it is necessary to reduce the hardness of the charging roll.

  However, the conventional charging roll has the following problems that hinder the reduction in hardness. That is, when the rubber layer constituting the charging roll is extrusion-molded, the rubber of the rubber layer shrinks and the smoothness of the extruded surface tends to be impaired. Therefore, in order to obtain smoothness of the extruded surface, usually a large amount of filler such as silica is blended in the rubber layer. This filler hardens the rubber layer. As a result, there has been a problem that the hardness of the roll surface is increased and the reduction of the hardness of the charging roll is hindered.

  Further, as the hardness of the roll surface increases as described above, the stress on the toner increases, so that the toner is easily crushed and the roll surface is soiled.

  The problem to be solved by the present invention is to provide a charging roll for electrophotographic equipment having a small diameter and low hardness. Another object is to provide a method for producing a charging roll for electrophotographic equipment.

  In order to solve the above problems, an electrophotographic apparatus charging roll according to the present invention is laminated on the outer periphery of a shaft body in order with at least a rubber elastic layer and a rubber tube layer in contact with each other. The gist is that a lubricant is contained in one or both of the rubber tube layers.

  In this case, the rubber elastic layer and the rubber tube layer are preferably made of non-foamed rubber.

  The outer diameter of the roll is 12 mm or less, the thickness of the rubber elastic layer is in the range of 0.5 to 2.9 mm, and the thickness of the rubber tube layer is in the range of 0.1 to 2.5 mm. It is desirable to be in

  Furthermore, the Asuka-C hardness of the roll surface in a state where the rubber elastic layer is formed on the outer periphery of the shaft body is in the range of 63 to 80, and the rubber elastic layer and the rubber tube layer are laminated on the outer periphery of the shaft body. The Asuka-C hardness of the roll surface in the state is preferably in the range of 65 to 82.

  On the other hand, the method for producing a charging roll for electrophotographic equipment according to the present invention comprises a step of forming a rubber elastic layer on the outer periphery of a shaft body and covering a rubber tube on the outer periphery of the rubber elastic layer, The gist is that a lubricant is contained in one or both of the rubber tubes.

  The charging roll for electrophotographic equipment according to the present invention is laminated on the outer periphery of the shaft body in order with at least the rubber elastic layer and the rubber tube layer being in contact with each other, and the surface of the rubber elastic layer is a rubber tube layer. Covered.

  Therefore, the rubber elastic layer can be reduced in filler for obtaining surface smoothness, and the hardness of the rubber elastic layer can be kept low. And since this rubber elastic layer softens the hardness of layers, such as a rubber tube layer laminated | stacked on the outer periphery, the roll surface becomes low hardness. Accordingly, since the hardness can be reduced even if the roll has a small diameter, the charging roll has a small diameter and a low hardness.

  At this time, since one or both of the rubber elastic layer and the rubber tube layer contains a lubricant, the rubber tube forming the rubber tube layer can be easily covered on the outer periphery of the rubber elastic layer, Excellent charge roll formability.

  In this case, if the rubber elastic layer and the rubber tube layer are each made of non-foamed rubber, the slip between the rubber elastic layer and the rubber tube is improved, and the moldability of the charging roll is excellent. Moreover, it becomes easy to control the dimensions of the rubber elastic layer and the rubber tube.

  And when the thickness of the rubber elastic layer is in the range of 0.5 to 2.9 mm and the thickness of the rubber tube layer is in the range of 0.1 to 2.5 mm, the diameter is reduced and the hardness is low. Excellent balance with conversion.

  Furthermore, the roll surface Asuka-C hardness in a state where the rubber elastic layer is formed on the outer periphery of the shaft body is in the range of 63 to 80, and the rubber elastic layer and the rubber tube layer are laminated on the outer periphery of the shaft body. When the Asker-C hardness of the roll surface in the state is in the range of 65 to 82, the roll surface has an appropriate elasticity, so that the chargeability is excellent.

  On the other hand, in the method for producing a charging roll for electrophotographic equipment according to the present invention, a rubber elastic layer is formed on the outer periphery of the shaft body, and a rubber tube is placed on the outer periphery of the rubber elastic layer. A lubricant is contained in one or both of the rubber tubes. Therefore, the charge roll is excellent in formability, and the productivity of a charge roll having a small diameter and low hardness is improved.

  Next, the charging roll for electrophotographic equipment according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a charging roll according to an embodiment of the present invention.

  As shown in FIG. 1, the charging roll 10 according to an embodiment is formed by laminating a rubber elastic layer 14, a rubber tube layer 16, and a surface layer 18 in this order on the outer periphery of a conductive shaft 12. The charging roll 10 is preferably a small-diameter charging roll having a roll outer diameter of 12 mm or less, more preferably 9 mm or less.

  In the charging roll according to the present invention, it is sufficient that at least the rubber elastic layer 14 and the rubber tube layer 16 are sequentially laminated on the outer periphery of the conductive shaft 12, and the surface layer 18 is formed. It does not have to be. Further, a resistance adjustment layer may be further formed immediately below the surface layer 18.

  Examples of the conductive shaft 12 include a metal core made of a metal solid body, a metal cylindrical body hollowed out inside, or a metal plated body thereof. The outer diameter of the cored bar is preferably 10 mm or less. More preferably, it is 8 mm or less, More preferably, it is 6 mm or less. Conversely, the outer diameter of the cored bar is preferably 4 mm or more. This is because if it is less than 4 mm, the strength tends to be insufficient.

  Examples of the rubber forming the rubber elastic layer 14 include butadiene rubber (BR), styrene-butadiene rubber (SBR), ethylene-propylene rubber (EPDM), silicone rubber (VMQ), nitrile rubber (NBR), isoprene rubber ( IR) and the like. These may be used alone or in combination.

  More preferred are butadiene rubber (BR), styrene-butadiene rubber (SBR), ethylene-propylene rubber (EPDM), and silicone rubber (VMQ). These materials are inexpensive, and the manufacturing cost of the charging roll 10 can be reduced.

  In addition, these materials have a low hardness compared to hydrin rubber (ECO, CO), acrylonitrile-butadiene rubber (NBR), and the like that have been conventionally used as rubber constituting the base of the roll. When the rubber elastic layer 14 is made of, for example, butadiene rubber (BR) or styrene-butadiene rubber (SBR), the hardness can be made lower than before.

The rubber elastic layer 14 may contain a conductive agent (an electronic conductive agent such as carbon black or an ionic conductive agent such as quaternary ammonium salt) in addition to the rubber. The content of the conductive agent is usually such that the volume resistivity of the rubber elastic layer 14 is preferably 1 × 10 ² to 1 × 10 ⁵ Ω · cm, more preferably 1 × 10 ³ to 1 × 10 ⁴ Ω · cm. What is necessary is just to adjust suitably so that it may become in the range of cm.

  In addition to the conductive agent, the rubber elastic layer 14 may be filled with a filler (filler), an extender, a reinforcing agent, a processing aid, a curing agent, a vulcanization accelerator, a crosslinking agent, a crosslinking aid, an oxidation as necessary. One or more various additives such as an inhibitor, a plasticizer, an ultraviolet absorber, a pigment, a silicone oil, an auxiliary agent, and a surfactant may be appropriately contained.

  The rubber elastic layer 14 preferably has a low filler content such as silica from the viewpoint of reducing the hardness. For example, the filler content is preferably 20 parts by weight or less with respect to 100 parts by weight of the rubber forming the rubber elastic layer 14. When the filler content is 20 parts by weight or less, the Asker C hardness of the roll surface in a state where the rubber elastic layer 14 is formed on the outer periphery of the conductive shaft 12 is easily set in the range of 63-80.

  When the filler in the rubber elastic layer 14 is reduced, the smoothness of the surface of the rubber elastic layer 14 is likely to be lowered. However, since the rubber elastic layer 14 is covered with the rubber tube layer 16, the smoothness of the surface of the rubber elastic layer 14. Has less influence on the smoothness of the surface of the charging roll 10. That is, even if the filler in the rubber elastic layer 14 is reduced, the smoothness of the surface of the charging roll 10 is not easily impaired.

  Therefore, the filler content in the rubber elastic layer 14 can be reduced and the hardness of the rubber elastic layer 14 can be kept low. When the hardness of the rubber elastic layer 14 is low, the hardness of the rubber tube layer 16 laminated on the outer periphery thereof is softened, so that the roll surface has a low hardness. Thereby, since the hardness can be reduced even if the roll has a small diameter, the charging roll 10 can be a roll having a small diameter and a low hardness.

  The thickness of the rubber elastic layer 14 is preferably in the range of 0.5 to 2.9 mm. This is because the surface hardness of the charging roll 10 can be lowered and the charging roll 10 can be made small in diameter. More preferably, it exists in the range of 0.8-2.5 mm.

  It is preferable that the Asker-C hardness of the roll surface in the state which formed the rubber elastic layer 14 in the outer periphery of the electroconductive shaft 12 exists in the range of 63-80. This is because the Asker-C hardness of the roll surface in a state where the rubber elastic layer 14 and the rubber tube layer 16 are laminated on the outer periphery of the conductive shaft 12 can be reduced to a low hardness in the range of 65 to 82.

  Examples of the rubber forming the rubber tube layer 16 include hydrin rubber (ECO, CO), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), and the like. These may be used alone or in combination.

  More preferred are hydrin rubber (ECO, CO) and acrylonitrile-butadiene rubber (NBR).

The rubber tube layer 16 may contain a conductive agent (an electronic conductive agent such as carbon black or an ionic conductive agent such as a quaternary ammonium salt). The content of the conductive agent is usually such that the volume resistivity of the rubber elastic layer is preferably 1 × 10 ² to 1 × 10 ⁵ Ω · cm, more preferably 1 × 10 ³ to 1 × 10 ⁴ Ω · cm. What is necessary is just to adjust suitably so that it may become in the range of cm.

  In addition to the conductive agent, the rubber tube layer 16 is filled with a filler (filler), an extender, a reinforcing agent, a processing aid, a curing agent, a vulcanization accelerator, a crosslinking agent, a crosslinking aid, an oxidation as necessary. You may contain 1 type, or 2 or more types of various additives, such as an inhibitor, a plasticizer, a ultraviolet absorber, a pigment, silicone oil, an adjuvant, and surfactant.

  The rubber tube layer 16 preferably contains a large amount of filler such as silica. This is because the surface smoothness of the rubber tube layer 16 can be obtained. For example, the amount of filler is preferably 25 parts by weight or more with respect to 100 parts by weight of rubber forming the rubber tube layer 16.

  The thickness of the rubber tube layer 16 is preferably in the range of 0.1 to 2.5 mm. This is because the surface hardness of the charging roll 10 can be lowered and the charging roll 10 can have a small diameter. More preferably, it is in the range of 0.2 to 1.5 mm.

  The rubber forming the rubber elastic layer 14 and the rubber tube layer 16 is preferably non-foamed rubber. Thereby, the slip between the rubber elastic layer 14 and the rubber tube layer 16 is improved, and the formability of the charging roll 10 is improved. Moreover, it becomes easy to control the dimensions of the rubber elastic layer 14 and the rubber tube layer 16.

  Here, a lubricant is contained in one or both of the rubber elastic layer 14 and the rubber tube layer 16. When the lubricant is contained, the friction between the rubber elastic layer 14 and the rubber tube layer 16 is reduced.

  Therefore, when the rubber tube 16 forming the rubber tube layer 16 is put on the outer periphery of the rubber elastic layer 14, the rubber tube 16 is less likely to be distorted. Thereby, the rubber tube 16 can be easily covered on the outer periphery of the rubber elastic layer 14, and the charging roll 10 is excellent in moldability. Further, the appearance of the charging roll 10 is also excellent.

  Further, as described above, when the amount of filler in the rubber elastic layer 14 is small, the rubber elastic layer 14 contracts when the rubber elastic layer 14 is extruded, and the surface skin is likely to be rough. If the surface of the rubber elastic layer 14 is rough, the rubber tube 16 is hardly covered with the outer periphery of the rubber elastic layer 14. Even in such a case, if one or both of the rubber elastic layer 14 and the rubber tube layer 16 contains a lubricant, the rubber tube 16 can be easily covered on the outer periphery of the rubber elastic layer 14.

  Examples of the lubricant include a normal phosphate ester lubricant, an aliphatic dibasic ester lubricant, and a phthalate ester lubricant.

  The addition amount of the lubricant is preferably in the range of 2.0 to 6.0 parts by weight with respect to 100 parts by weight of rubber forming the rubber elastic layer 14 or the rubber tube. If the amount is less than 2.0 parts by weight, the effect of adding the lubricant is difficult to be exhibited. On the other hand, if the amount exceeds 6.0 parts by weight, bleeding of the lubricant tends to occur. More preferably, it is in the range of 2.0 to 5.0 parts by weight.

  The thickness of the surface layer 18 is preferably adjusted as appropriate so that it is preferably in the range of 3 to 18 μm, more preferably in the range of 5 to 15 μm.

  Examples of the polymer forming the surface layer 18 include urethane resin, polyamide resin, acrylic resin, acrylic silicone resin, butyral resin, alkyd resin, polyester resin, fluororubber, fluororesin, a mixture of fluororesin and fluororubber, and silicone resin. Examples thereof include acrylic-modified silicone resins, silicone-modified acrylic resins, fluorine-modified acrylic resins, nitrile rubber, urethane rubber, and resins obtained by crosslinking these. These may be used alone or in combination. In particular, from the viewpoint of excellent wear resistance, a crosslinked urethane resin, an acrylic resin, an acrylic silicone resin, a fluorine-modified acrylic resin, and the like can be suitably used.

  The surface layer 18 may contain a conductive agent (electronic conductive agent and / or ionic conductive agent). Moreover, you may contain suitably 1 type, or 2 or more types of various additives, such as a roughness formation agent, a plasticizer, and a leveling agent, as needed.

  When a resistance adjusting layer is provided under the surface layer 18, one layer or two or more layers may be provided as necessary. Examples of the polymer forming the resistance adjusting layer include hydrin rubber (ECO), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), and the like.

  The resistance adjusting layer may contain a conductive agent (an electronic conductive agent and / or an ionic conductive agent). If necessary, fillers, extenders, reinforcing agents, processing aids, curing agents, vulcanization accelerators, crosslinking agents, crosslinking aids, antioxidants, plasticizers, UV absorbers, pigments, silicone oils In addition, one or more various additives such as an auxiliary agent and a surfactant may be appropriately contained.

  It is preferable that the charging roll 10 has the rubber elastic layer 14, the rubber tube layer 16, and the like configured as described above, so that the roll surface has an Asuka-C hardness within a range of 65 to 82.

  Next, a method for manufacturing a charging roll according to the present embodiment (hereinafter sometimes referred to as “the present manufacturing method”) will be described.

  In this manufacturing method, the rubber elastic layer 14 is formed on the outer periphery of the conductive shaft 12. Specifically, for example, a method of extruding a material for forming the rubber elastic layer 14 on the surface of the conductive shaft 12 to which an adhesive, a primer or the like is arbitrarily applied, and the conductive shaft 12 is hollow in a roll molding die It is possible to form the rubber elastic layer 14 on the outer periphery of the conductive shaft 12 by a method of removing the mold after injecting the material forming the rubber elastic layer 14 coaxially, heating and curing, and then demolding. it can.

  Next, a rubber tube 16 is prepared. The rubber tube 16 may be used after being molded by extrusion, or a commercially available rubber tube may be used.

  Next, the rubber tube 16 is placed on the outer periphery of the formed rubber elastic layer 14 to form the rubber tube layer 16. FIG. 2 is a view for explaining an example of a process of covering the rubber elastic layer 14 with the rubber tube 16.

  As shown in FIG. 2, for example, a method of inserting the conductive shaft 12 formed with the rubber elastic layer 14 into the rubber tube 16 can be employed. Conversely, the rubber tube 16 may be moved to the outer periphery of the rubber elastic layer 14 formed on the outer periphery of the conductive shaft 12 so that the rubber tube 16 is covered on the outer periphery of the rubber elastic layer 14.

  In order to cover the rubber tube 16, for example, the rubber tube 16 is inserted into a hard cylinder, the rubber tube 16 is expanded in the cylinder, and then the conductive shaft 12 on which the rubber elastic layer 14 is formed is attached to the rubber tube. 16 may be inserted.

  The use of a hard cylinder has advantages such that the rubber tube 16 can be uniformly expanded in the axial direction and the circumferential direction thereof, and the rubber tube 16 does not expand more than necessary. Note that the method of covering the rubber tube 16 is not limited to the method using a cylinder.

  The hard cylinder may be a cylinder or a square cylinder. Preferably, it is a cylinder in that the rubber tube can be uniformly expanded in the circumferential direction. In order to expand the rubber tube 16 in the cylindrical body, a cylindrical body having an inner diameter larger than the outer diameter of the rubber tube 16 may be used.

  In order to expand the rubber tube 16, for example, the rubber tube 16 may be inflated by supplying gas into the rubber tube 16 in a state where the rubber tube 16 is inserted into a hard cylindrical body. The type of gas is not particularly limited, and examples thereof include air and nitrogen gas. Further, the pressure of the gas to be supplied may be appropriately selected.

  In addition, the method of expanding the rubber tube 16 is not limited to the method of expanding by the gas. In addition, the rubber tube 16 can be expanded by using an instrument.

  The inner diameter of the rubber tube 16 is preferably smaller than the outer diameter of the rubber elastic layer 14. This is because the rubber tube 16 can be brought into close contact with the surface of the rubber elastic layer 14 when the rubber tube 16 is put on the outer periphery of the rubber elastic layer 14.

  Specifically, the difference between the inner diameter of the rubber tube 16 and the outer diameter of the rubber elastic layer 14 is preferably in the range of 0.1 to 0.3 mm. If it is less than 0.1 mm, the adhesiveness between the rubber elastic layer 14 and the rubber tube layer 16 is lowered. On the other hand, if it exceeds 0.3 mm, it is difficult to cover the rubber tube 16 on the outer periphery of the rubber elastic layer 14.

  Here, a lubricant is contained in one or both of the rubber elastic layer 14 and the rubber tube 16. When the lubricant is contained, friction between the rubber tube layer 16 and the rubber elastic layer 14 is reduced.

  Therefore, when the rubber tube 16 is put on the outer periphery of the rubber elastic layer 14, the rubber tube 16 is less likely to be distorted. Thereby, the rubber tube 16 can be easily covered, and the productivity of the charging roll 10 is improved.

  The surface layer 18 can be formed on the outer periphery of the rubber tube layer 16 by, for example, a method of coating a material for forming the surface layer 18 on the outer periphery of the rubber tube layer 16. Examples of the coating method include a roll coating method, a dipping method, and a spray coating method. After coating the material, the coated material is dried (cured) to form the surface layer 18.

  When the resistance adjustment layer is formed under the surface layer 18, for example, the resistance adjustment layer is formed by performing an operation according to a method of forming the rubber elastic layer 14 or a method of forming the surface layer 18. Can do.

  Hereinafter, the present invention will be described in detail using examples.

Example 1
<Conductive shaft>
A solid cylindrical conductive shaft made of iron having an outer diameter of 6 mm and a length of 250 mm and having a surface plated with Ni was prepared.

<Preparation of rubber elastic layer composition>
100 parts by weight of butadiene rubber (BR) (manufactured by JSR Corporation, “JSR HP752”), 15 parts by weight of carbon black (manufactured by Cabot Japan Co., Ltd., “Show Black N220”), 1 part by weight of stearic acid, , 5 parts by weight of zinc oxide (ZnO), 2 parts by weight of a lubricant (a normal phosphate ester lubricant, tributyl phosphate (O = P (OC ₄ H ₉ ) ₃ ), and 0.8 parts by weight of powder sulfur, A rubber elastic layer composition was prepared by kneading with rubber.

<Preparation of rubber tube layer composition>
70 parts by weight of epichlorohydrin rubber (ECO) (manufactured by Nippon Zeon Co., Ltd., “Hydrin C2000”), 30 parts by weight of acrylonitrile-butadiene rubber (NBR) (manufactured by Nippon Zeon Co., Ltd., “Nipol DN101”), 1 part by weight of stearic acid, 5 parts by weight of zinc oxide (ZnO), 50 parts by weight of silica (manufactured by Nippon Silica Kogyo Co., Ltd., “Nipseal VN3”), 0.8 part by weight of powdered sulfur, rubber with a kneader A rubber tube layer composition was prepared by kneading.

<Preparation of surface coating solution>
100 parts by weight of N-methoxymethylated nylon (made by Teikoku Chemical Industry Co., Ltd., “Tresin EF30T”), 30 parts by weight of trimethylol melamine (manufactured by Sumitomo Chemical Co., Ltd., “Sumikaflex M3”), carbon black ( 15 parts by weight of Ketjen Black International (“Ketjen Black EC”) was mixed and stirred in 500 parts by weight of a methanol-toluene mixed solution (methanol: toluene = 7: 3) to prepare a surface coating solution.

<Preparation of charging roll>
The rubber elastic layer composition is extruded on the surface of the conductive shaft, oven vulcanized (180 ° C., 40 minutes), and the outer periphery of the conductive shaft has an outer diameter of 7.8 mm and a thickness of 0.9 mm. The rubber elastic layer was formed.

  Next, the rubber tube layer composition was formed into a tube by extrusion, and oven vulcanized (180 ° C., 50 minutes) to form a rubber tube having an inner diameter of 7.6 mm and a thickness of 0.4 mm.

  Next, the rubber tube was inserted into a cylinder having an inner diameter of 10 mm, and the conductive shaft having the rubber elastic layer formed therein was inserted into the rubber tube while the rubber tube was inflated with air. Air supply was stopped, the rubber elastic layer and the rubber tube were brought into close contact with each other, and a rubber tube layer was formed on the outer periphery of the rubber elastic layer.

  Next, the surface layer coating solution was applied on the surface of the rubber tube layer by a roll coating method and dried to form a surface layer on the outer periphery of the rubber tube layer. As described above, the charging roll according to Example 1 was manufactured.

(Examples 2-3)
In the preparation of the rubber elastic layer composition of Example 1, the charging rolls according to Examples 2 to 3 were produced in the same manner as Example 1 except that the blending amount of the lubricant was changed to the amount shown in Table 1. did.

Example 4
In the preparation of the rubber elastic layer composition of Example 1, the blending amount of the lubricant was changed to the amount shown in Table 1, and in the preparation of the charging roll of Example 1, the outer diameter of the conductive shaft was 9.2 mm. Except for the point where a 1.6 mm thick rubber elastic layer was formed, the inner diameter was 9.0 mm, the rubber tube was 0.4 mm thick, and the rubber tube was inserted into a cylinder with an inner diameter of 12 mm. In the same manner as in Example 1, a charging roll according to Example 4 was produced.

(Example 5)
In the preparation of the rubber elastic layer composition of Example 1, the blending amount of the lubricant was changed to the amount shown in Table 1, and in the production of the charging roll of Example 1, the outer diameter of the conductive shaft was 11.2 mm. , Except that a 2.6 mm thick rubber elastic layer was formed, an inner diameter was 11.0 mm, a rubber tube having a thickness of 0.4 mm was formed, and this rubber tube was inserted into a cylinder having an inner diameter of 14 mm. In the same manner as in Example 1, a charging roll according to Example 5 was produced.

(Comparative Example 1)
In the preparation of the rubber elastic layer composition of Example 1 above, except for the points shown in Table 1, the point where the thickness of the rubber elastic layer was 1.3 mm, and the rubber tube layer was not formed, Example 1, a charging roll according to Comparative Example 1 was produced. That is, the charging roll according to Comparative Example 1 is formed by laminating a rubber elastic layer and a surface layer on the outer periphery of the conductive shaft.

(Comparative Example 2)
In the preparation of the rubber elastic layer composition of Example 1, a charging roll according to Comparative Example 2 was produced in the same manner as in Example 1 except that no lubricant was blended.

<Measurement method>
(Asuka-C hardness)
Using a rubber hardness meter (Polymer Keiki Co., Ltd., “Asuka-C”), it was measured according to JIS K7312. The Asker C hardness is an average value of values measured at three locations at equal intervals in the circumferential direction in the center of the roll surface length. In addition, the measurement temperature is 25 ° C. for all.

(Nip width)
The nip width was measured by the method shown in FIG. That is, each charging roll is incorporated in a commercially available cartridge (manufactured by Hewlett-Packard Co., Ltd., “HP LBP-4650”), and the photosensitive drum 20 and the charging roll 10 are not rotated in an environment of 23 ° C. × 53% RH. In addition, voltages of 3000 Hz, 2.5 kVpp, and −600 V were applied from the outside for 5 minutes (FIG. 3A). A nip width A (FIGS. 3 (c) and 3 (d)) formed between the discharge widths B and B on the surface of the charging roll 10 due to the discharge from the charging roll 10 to the photosensitive drum 20 (FIG. 3 (b)). The measurement was made at the center and at the end of each. FIG. 3D is an enlarged view of a portion X in FIG.

(Photosensitive drum surface potential)
Each charging roll is incorporated into a commercially available cartridge ("HP LBP-4650" manufactured by Hewlett-Packard Co., Ltd.), and is rotated from the outside while rotating both the photosensitive drum and the charging roll in an environment of 15 ° C x 10% RH. Only the power supply (-800V, -900V, -1000V, -1100V) was applied. At this time, as shown in FIG. 4, a probe 22 of a surface electrometer “MODEL-370” manufactured by Trek Japan Co., Ltd. is disposed at a position 2 mm away from the photosensitive drum, and the surface of the central portion of the photosensitive drum in the dark. The potential was measured.

<Evaluation of each charging roll>
About each charging roll which concerns on an Example and a comparative example, surface hardness, a moldability, and cost were evaluated. The evaluation criteria for formability are shown below.

(Formability)
The workability when the rubber tube was put on the outer periphery of the rubber elastic layer was evaluated. That is, the case where a conductive shaft having a rubber elastic layer formed in a rubber tube could be inserted was regarded as acceptable. At this time, the case where almost no distortion occurred in the covered rubber tube was evaluated as “「 ”, and the case where some distortion occurred in the covered rubber tube was evaluated as“ good ”. On the other hand, the case where it was difficult to insert the conductive shaft into the rubber tube was determined as “Fail”.

  Further, the influence of the hardness of the roll surface on the product performance was evaluated from the viewpoint of image evaluation after the durability test and roll stain after the durability test. The evaluation criteria are shown below.

(Image evaluation after endurance image output test)
As a durability image output test, each charging roll was incorporated into a commercially available color laser printer (manufactured by Hewlett-Packard Co., Ltd., “HP LBP-4650”), and character image output was performed in an environment of 15 ° C. × 10% RH 6500 Sheets (A4 size) were performed. After the endurance image output test, one cyan halftone image was prepared and visually confirmed. As a result, the case where there was no horizontal streak was regarded as a pass “◯”, and the case where a horizontal streak was generated was regarded as a disqualified “x”.

(Roll dirt after endurance image output test)
After the durability image output test, the appearance of the charging roll was confirmed. That is, when such an endurance test is performed, a phenomenon in which an external additive such as silica removed from the toner adheres to the roll surface occurs.

  Here, after the endurance image output test, there is little white powder on the roll surface, or there is a part where the white powder is slightly on the roll surface, or the white powder is slightly on the entire roll surface. The one with the mark on the mark was regarded as acceptable. Of these, those that have almost no white powder on the roll surface are marked as “Excellent”, and there are parts that have a slight white powder on the roll surface, or there is a slight white powder on the entire roll surface. Good ones were marked as “Good”. On the other hand, after the durability evaluation, white powder adhered to the entire surface of the roll, and those that exceeded white and looked white were regarded as rejected “x”.

  Table 1 shows a summary of the blending and evaluation results of the rubber elastic layer, rubber tube layer, and surface layer forming material of each charging roll.

  The charging roll according to Comparative Example 1 is an example of a conventional charging roll, does not have a rubber tube layer, and is formed by laminating a rubber elastic layer and a surface layer on the outer periphery of a shaft body. A large amount of silica is blended in the rubber elastic layer in order to obtain smoothness of the extruded surface. Therefore, it can be seen that the hardness of the rubber elastic layer is high and the hardness of the surface of the charging roll is high (from Table 1, Asuka-C hardness of the roll surface = 85).

  Further, in the configuration of the charging roll according to Comparative Example 1, the amount of relatively expensive hydrin rubber used is increased, so that the material cost is increased.

  The charging roll according to Comparative Example 2 has the rubber tube layer on the outer periphery of the rubber elastic layer, but neither the rubber elastic layer nor the rubber tube layer contains a lubricant. For this reason, it becomes difficult to cover the outer periphery of the rubber elastic layer with a rubber tube, which indicates that the moldability is poor.

  On the other hand, the charging roll according to Examples 1 to 5 has a rubber tube layer on the outer periphery of the rubber elastic layer. A large amount of silica is blended in the rubber tube layer in order to obtain smoothness of the extruded surface, but silica is not blended in the rubber elastic layer. Moreover, SBR and BR are used for the rubber of the rubber elastic layer, and the hardness is lower than that of ECO used for the rubber tube layer.

  For this reason, the hardness of the rubber elastic layer is kept low (from Table 1, the ASCII surface hardness of the roll surface in a state where the rubber elastic layer is formed on the outer periphery of the conductive shaft = 75.5 to 76), a comparative example. 1 is smaller than the hardness of the rubber elastic layer. This rubber elastic layer softens the hardness of the rubber tube layer laminated on the outer periphery thereof. As a result, the hardness of the roll surface could be reduced, and it was confirmed that the hardness of the roll surface was smaller than that of the conventional charging roll (from Table 1, Asuka-C hardness = 79-80).

  In particular, in Examples 4 and 5, the outer diameter of the roll was increased by increasing the thickness of the rubber elastic layer and the like as compared with Example 1, and the hardness of the rubber elastic layer was further reduced, and the hardness of the roll surface was reduced. Is even smaller.

  In addition, although the charging roll which concerns on Examples 1-5 does not mix | blend silica in the rubber elastic layer, the outer periphery is covered with the rubber tube layer. Therefore, the smoothness of the charging roll surface is ensured by the smoothness of the rubber tube layer surface.

  In addition, if the configuration of the charging roll according to Examples 1 to 5, the amount of relatively expensive hydrin rubber or nitrile rubber is reduced and the use of relatively inexpensive butadiene rubber or the like reduces the material cost. can do. Therefore, the material cost is also excellent.

  Furthermore, the charging roll according to Examples 1 to 5 includes a lubricant in the rubber elastic layer. Therefore, when the rubber tube is put on the outer periphery of the rubber elastic layer, the friction between the rubber elastic layer and the rubber tube is reduced. Thereby, it became easy to cover a rubber tube on the outer periphery of the rubber elastic layer, and it was confirmed that the moldability was excellent.

  Next, regarding the influence of the hardness of the roll surface on the product performance, the nip width and the surface potential of the photosensitive drum surface are larger in Examples 1 and 3 than in Comparative Example 1. Therefore, it can be seen that the charging roll according to Examples 1 and 3 is superior in charging property to the charging roll according to Comparative Example 1. In addition, it was confirmed that the charging rolls according to Examples 1 and 3 were superior to the charging roll according to Comparative Example 1 in the image after the endurance image forming test and were less likely to cause roll contamination. Thus, it was confirmed that when the charging roll according to Examples 1 and 3 was incorporated into a product, an excellent function was exhibited.

  Further, in Examples 4 and 5 in which the roll outer diameter is larger than that in Example 1, the nip width and the surface potential of the photosensitive drum surface are larger than those in Example 1, and the chargeability is more excellent. I understand that. It was confirmed that the image after the endurance image output test was excellent and that roll contamination was less likely to occur.

  In addition, the surface hardness of the charging roll according to Example 2 is as small as the surface hardness of the charging roll according to Example 1. Therefore, also in the charging roll according to Example 2, it is considered that the nip width and the surface potential of the surface of the photosensitive drum are increased to the same extent as the charging roll according to Example 1. Further, like the charging roll according to Example 1, it is considered that the image after the durability test is excellent, and roll contamination is less likely to occur. Therefore, it is considered that an excellent function is exhibited even when the charging roll according to Example 2 is incorporated into a product.

  In this embodiment, an example in which a lubricant is contained in the rubber elastic layer is shown, but when a lubricant is contained in the rubber tube, the lubricant is contained in both the rubber elastic layer and the rubber tube. Of course, the same effect can be obtained even in this case.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said Example at all, A various change is possible in the range which does not deviate from the summary of this invention.

It is sectional drawing showing the charging roll which concerns on one Embodiment. It is a figure explaining an example of the process of putting a rubber tube on the outer periphery of a rubber elastic layer. It is a figure explaining the method to measure a nip width. It is a figure explaining the method to measure the photosensitive drum surface potential.

Explanation of symbols

10 Charging roll 12 Conductive shaft 14 Rubber elastic layer 16 Rubber tube layer 18 Surface layer

Claims (5)

On the outer periphery of the shaft body, at least the rubber elastic layer and the rubber tube layer are sequentially laminated in a state of being in contact with each other,
A charging roll for electrophotographic equipment, wherein a lubricant is contained in one or both of the rubber elastic layer and the rubber tube layer.   The charging roll for an electrophotographic apparatus according to claim 1, wherein the rubber elastic layer and the rubber tube layer are each made of non-foamed rubber. Roll outer diameter is 12 mm or less,
The rubber elastic layer has a thickness in the range of 0.5 to 2.9 mm,
The charging roll for an electrophotographic apparatus according to claim 1 or 2, wherein the rubber tube layer has a thickness in a range of 0.1 to 2.5 mm. Asker-C hardness of the roll surface in a state where the rubber elastic layer is formed on the outer periphery of the shaft body is in a range of 63 to 80,
4. The Asker C hardness of the roll surface in a state where the rubber elastic layer and the rubber tube layer are laminated on the outer periphery of the shaft body is in the range of 65 to 82. 5. The charging roll for electrophotographic equipment as described. Forming a rubber elastic layer on the outer periphery of the shaft, and covering the outer periphery of the rubber elastic layer with a rubber tube;
A method for producing a charging roll for electrophotographic equipment, wherein a lubricant is contained in one or both of the rubber elastic layer and the rubber tube.

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